Theoretical insights into interfacial-layer control of Fermi-level depinning and dipole engineering for Schottky barrier height reduction in NiSi/Si systems

Metal-semiconductor contact resistance poses a critical challenge due to the reduced contact area in next-generation semiconductor devices, which can be tuned by the Schottky barrier heights (SBHs). However, the strong surface Fermi-level pinning (FLP) introduces the uncontrolled SBHs for conventional doping strategies. In this study, we propose the interfacial-layer control of Fermi-level depinning and dipole engineering and demonstrate the critical effect of TiO2 as the interfacial layer for reducing SBHs in the NiSi/Si system. Our theoretical results reveal that a 0.7 nm TiO2 interlayer is required to achieve the low SBH of 0.12 eV compared with the intrinsic system of 0.65 eV. FLP mitigation through metal-induced gap state reduction remains foundational for SBH control, and the dipole charge effect provides an additional degree for interfacial energy band tailoring. Even though the SBHs exhibit the higher values depending on the different oxygen vacancy sites and concentration, it is still lower than that of pristine systems, demonstrating its feasibility in reducing SBHs. These findings provide solid foundation for minimizing contact resistance in state-of-the-art semiconductor technologies.